I only have small ornamental trees, 15'-ish. The best are my serviceberry and my 'Princess Kay' plum. Nice blossoms on both, no litter/suckers/seedlings and the serviceberry fall color is WONDERFUL. They're not shade trees per se but maybe worth looking into. Acer maples are great too, especially for shade. I love ours but it does make a lot of seedlings. I just throw mulch on them when they're tiny and it smothers them right out so they haven't been a problem for me.

Sadly, ash trees are quarantined in your area.

AVOID: Aspen, cottonwood, silver maple.

Here's PlantSelect suggestions:
http://www.plantselect.com/plant-search/?query=&=Search&adv_10=t&adv_27=t&=Search&sort=botanic

Good luck!

I did a search and saw some of your earlier posts...do you still have that big elm tree?

Earlier you mentioned wanting to plant a plum tree, and I think some sort of fruit tree would be a good idea, most need lots of sun and are supposed to grow fast and would respond well to pruning to keep them 20' or shorter. But I think some kinds of plums take many years to bear fruit, much longer than other kinds of fruits, and you may need two to get pollination, I would ask on the Fruit forum.

I'm no expert, I planted 12 fruit trees of various kinds ths year and we will see how they do. But no plums, and I'm starting to regret that. There will be some work with fruit trees but hopefully it would be worth it.

Yes, we, or the city of Longmont, still have the 100 year old elm tree out front. The city just trimmed it which was scary, but my husband talked to them before hand about what they were going to do and all is good. We also have three Ash trees in the back yard - my husband is treating them hoping that they won't get the Emerald Ash bug.

I still would like a plum. I will check those out and the Serviceberry.
Thanks,
Diane